ORLANDO — After weeks of sniping at each other on the campaign trail, Marco Rubio and Patrick Murphy took swipes at each other Monday night in the first of two scheduled U.S. Senate debates before Election Day.

Over 57 heated minutes, Murphy, the Democratic challenger, repeatedly attacked Rubio for his absenteeism during his first term as U.S. senator and for his support of Republican presidential nominee Donald Trump. Rubio highlighted embellishments Murphy made to his academic and professional resumes, and derided his "record of doing absolutely nothing" in two congressional terms.

Murphy — lagging in every poll since June and still lacking name recognition among a sizable portion of likely voters — needed to shine Monday in front of his largest audience ever. Except for a few moments where he appeared rattled and some exchanges where he gave repetitive answers, he held his own against the more battle-tested Rubio.

The two covered a gamut of policy issues that included immigration, foreign policy, gun control, climate change and health care. But the first 15 minutes of the debate at the University of Central Florida was dominated by the presidential race.

Rubio spent several minutes on the defensive, having to explain why he is still backing Trump while simultaneously not defending him once. In the past 10 days, Trump has been accused by several women of sexual assault in the wake of a leaked 2005 Access Hollywood video that showed Trump bragging about kissing and groping women without their consent.

Rubio, 45, called Trump a "horrifying choice" and "not the most inspirational choice," but said Democrats had, in Hillary Clinton, "nominated someone who repeatedly violated federal law" and "who has a 30-year record of scandal and outrage."

"It's pretty clear Donald Trump is not my first choice or even my 10th choice to be the nominee of the Republican Party; 14 million voters in the Republican primaries chose differently," Rubio said. "One of the reasons why I changed my mind and ran for re-election is because I know that no matter who wins this election, you are going to need people in the United States Senate willing to stand up to the next president."

Murphy, 33, is supporting Clinton without apology, saying he trusts her "100 percent" despite a scandal about a private email server that she used while secretary of state. When asked why Floridians should trust him when polls show most of them don't trust Clinton, Murphy pivoted to stock answers before shifting back to criticizing Trump.

Near the end of the debate, Rubio grew frustrated with Murphy's repeated assertions that Rubio doesn't support women and fired back in personal terms. He brought up an old photo of Murphy, which shows him with his arm around a woman, appearing to grab her breast. GOP activists have circulated the photo on Twitter for weeks.

"You're the one that posted a picture four years ago on Facebook of you groping a woman. That's inappropriate behavior," Rubio said.

After the debate, Murphy campaign spokeswoman Galia Slayen said in an email that the photo was of "a former girlfriend at dinner." Mentioning the photo was "an act of desperation" by Rubio, Slayen said.

Rubio also had Murphy pinned during several other points during the debate, getting in jabs about how Murphy started his political career four years ago and how Murphy described himself as a certified public accountant and small business owner.

"You changed your name, changed your party and moved from South Beach to West Palm Beach to run for Congress. That's not a flip-flop; that's a metamorphosis," Rubio said at one point.

"You're the king of flip-flops," Murphy retorted.

In another tense exchange, Rubio referenced the environmental services company Murphy started as a subsidiary to his father's billion-dollar construction company. "It's not that hard to open a small business when your dad opens it for you," Rubio said.

"I never tried to hide that … you're making things up," Murphy said.

"No, I'm not the one who makes things up," Rubio quickly countered.

Murphy defended his resume embellishments by insisting again that all of the attacks against him had been "debunked" by independent fact checkers. Some have, but not all, and Murphy remains carefully nuanced in how he describes his credentials.

Many of Murphy's responses were pulled from his routine stump speech, including a stock line that Rubio "continues to put his own political ambition ahead of what's best for Florida."

But when moderators asked him about Republicans' criticism of his wealthy upbringing, Murphy had a fresh response.

"An attack on my dad is an attack on the American dream," Murphy said, channeling a theme Rubio uses when describing his own roots.

In another signature moment, Rubio quashed a persistent attack by Murphy by finally offering a definitive answer to whether he'd commit to serving a full term in office, if re-elected.

"I'm going to serve six years in the Senate, God willing, and I'm looking forward to it," Rubio said. When he was asked if he would run for president again, though, Rubio evaded and repeated that he'd serve six years in the Senate.

ABC News' chief White House correspondent, Jonathan Karl, moderated the one-hour debate. Questions were posed by Karl and a panel of Florida journalists: anchors Greg Warmoth and Nancy Alvarez of WFTV-Ch. 9 in Orlando, and Marc Caputo of Politico. WFTV, in partnership with ABC News, Politico and Cox Media Group, sponsored the event.

The second — and potentially final — debate between Murphy and Rubio will be Oct. 26 at Broward College, sponsored by Leadership Florida and the Florida Press Association.

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